3. Large-diameter welded pipe production unit

The production methods of large-diameter longitudinal submerged arc welded pipes (20-64in) for oil and gas transmission pipelines mainly include UOE method, RBE method, C forming method, JCOE method, HU-METAL method and full row roll forming method. Among the various forming methods, the steel pipe produced by the UOE method has the best quality and the highest reliability, but due to the huge investment in the construction of UOE units, it has no longer been built after entering the 80s of the 20th century. The roll bending process, which was originally mainly used for the production of large-diameter structural pipes (with an outer diameter of up to 4000mm), has been greatly improved in terms of performance and reliability after a series of transformations, so it is used to produce pipes for oil and gas transportation. Due to the flexibility of the bending process and the lower equipment investment than the UOE unit, it has been popularized and applied in some developing countries, which is the RBE method that has been widely recognized. According to statistics, since the 90s of the 20th century, 13 sets of large-diameter longitudinal submerged arc welded pipe production units have been built abroad, of which one is an RBE unit. In addition, in recent years, the German company SMS-Demng has developed a PFP forming method for the production of large-diameter longitudinal submerged arc welded pipes, and has been successfully applied to three factories (one of which can produce large-diameter thick-walled stainless steel pipes). In recent years, large-diameter spiral submerged arc welded pipe production units are still under construction in some countries, not only for the production of structural pipes, but also for the production of line pipes for oil and gas transportation. The maximum steel grade of the oil and gas transmission pipe produced has reached X80.